20 
S. 3JLETHOD OF IXFECTIOX. 
The life history of the organisms of malaria and Texas fever natu- 
rally suggested that some insect was concerned in the transmission of 
the disease. On investigation it was found that the ticks appeared in 
the valley about the last of February, but were inactive until the 
middle of March or first of April, the first cases of fever appearing 
about the last of March. The ticks begin to diminish greatly in 
number from about June 1. and after the middle of July very few are 
seen; the cases of fever also begin to diminish about Jime 1. the latest 
date on which the disease has been known to occur being July 20. 
Mo>squitoes do not appear in the valley until after the first cases of 
fever develop, and remain some time after the last cases appear. 
Bedbugs and other house insects. I think, were well excluded, by the 
fact that there has never been known an instance in which two cases 
occurred the same year in the same house. 
On a closer study of the cases of spotted (tick) fever it was always 
found that there was a history of tick bites about one week before the 
onset. In four cases there was a history of a single bite two. three, 
five, and seven days, respectively, before the initial symptoms. The 
usual time between the bite and the onset of the fever is about seven 
days. If the tick transmits the disease, it may be asked. Why do not 
more persons become infected, and why is the infection confined to 
the west bank of the Bitter Boot River ' I think this may be answered 
by the very obvious fact that the tick is unable to travel any great 
distance, unless carried on some person or object. Again, it is very 
unusual for a tick to bite a person and not be discovered in a short 
while, and the result is the death of the tick. If. as in Texas fever, 
the development of the parasite takes place in the female tick and the 
young ticks transmit the infection, the very small nmnber of ticks 
which escape detection on persons explains the small number of infected 
ticks. Where do the female ticks get their infection ' I examined a 
recovered case twenty-four days after discharge by the physician and 
had no trouble in finding the parasite in the fresh blood. This child 
had been out of doors for over two weeks, and if a female tick (ticks 
were cpfite numerous near the hoiioc) had bitten her and escaped 
destruction the parasites in the blood taken in by the tick would have 
undergone development and the young ticks, when hatched out, would 
be ready to infect prospective victims. 
While the above facts and conclusions tend strongly to the belief 
that the ticks are necessary for the transmission of the disease, the 
actual fact can not be proved scientifically until carefully controlled 
experiments are made on nonimmune persons. 
